The proposed research seeks to analyze functions of the amygdaloid complex and hippocampal formation in the plasticity of appetitive behavior of rats through electrophysiological analyses of unit activity in these structures. The strategy is to examine separately unit response patterns to conditional and unconditional types of stimuli and then to analyze interrelationships that develop as a function of classical and instrumental conditioning paradigms and also to assess the significance of motoric patterns that may be associated with changes in unit response. A system for intraoral injection of fluid will be used in the freely-moving animal to which response patterns to rewarding and aversive gustatory stimuli will be examined. An analysis will be made of the extent to which motivational properties of the stimuli influence unit responses. Response patterns to conditional classes of stimuli, i.e., tones, lights, will be examined in the context of on-going appetitive behavior in which unit activity can be related to behavioral and electrophysiological components of the orienting response and also in relation to background patterns of unit activity that may vary in relation to specific components of the appetitive behavior. Differential classical conditioning, utilizing oral injections of rewarding and aversive gustatory stimuli as the UCS will be employed to assess plasticity of unit activity so that response patterns to both CS and UCS can be examined in relation to one another and also in relation to hippocampal EEG which provides a measure of arousal and associated motoric patterning of activity. Similar analyses will be performed to study the behavior of units responsive to rewarding intraoral injection of fluid during antecedent appetitive behavior leading to the reinforcement. In the final stage of the work, it is planned to utilize hippocampal EEG state as a contingent condition in controlling presentation of rewarding UCS to a CS in order to determine to what extent conditioned patterns of motoric activity influence conditioned patterns of unit response to a CS. The test conditions should permit closer assessment to the functional significance of plasticity of unit activity in limbic structures than has formerly been the case.